Sliding sleeves, are widely used in a variety of hydrocarbon production systems. A sliding sleeve typically includes a tubular outer housing having threaded connections at one or both ends for connection to a tubing string. The insert is axially movable with respect to the outer housing. Embodied as a valve, the outer housing also includes one or more flow ports. Inside the housing, a sleeve mechanism, also known as an insert, is arranged to slide axially within the outer housing. The insert also comprises one or more flow ports. The insert can be positioned to align the flow ports in the sleeve with the flow ports in the housing, which will allow fluid flow through the sliding sleeve valve. Fluid flow can be from the inside or outside of the valve. Alternatively, the insert can be positioned with respect to the sleeve so that the flow ports are not aligned, thereby preventing fluid flow through the sliding sleeve valve.
The basic concept can be embodied to perform other functions, which will not be discussed in detail in this disclosure. For example, in some embodiments, the insert may not have flow ports, but may be arranged to either block the flow ports in the outer housing or not, thereby permitting flow or not. Sliding sleeve devices embodied as valves are disclosed in U.S. Patent Application Ser. No. 60/908,616 filed Mar. 28, 2007 and Ser. No. 12/030,036 filed Feb. 12, 2008, both of which are incorporated herein in their entirety.
In many operation and production applications, it is desired to determine the condition (i.e., whether open or closed) of one or more sliding sleeve in a tubing string within the borehole. Prior art systems include a shifting tool that is passed through the sliding sleeve. The shifting tool engages an open or a closed mechanism, thereby indicating whether the sliding sleeve is open or closed.
Other prior art mechanical tools have been developed that “feel” for a gap behind the insert to determine if the sliding sleeve is open or closed. A problem with these approaches is that the relatively subtle feel of these approaches, which takes the form of mechanical feedback, can in many cases, be difficult to detect and/or properly interpret.
U.S. patent application Ser. No. 12/030,036, previously entered into this application by reference, discloses a sliding sleeve borehole tool having one or more housing magnets affixed to an outer housing and one or more insert magnets affixed to an insert. A casing collar locator (CCL) tool can be conveyed or “logged” through the insert to detect the relative axial positions of the housing magnets and the insert magnets. The relative position of the magnets can then be used to ascertain the position of the insert within the housing, and thus whether the sliding sleeve is in the open or closed condition. In other embodiments of this sliding sleeve tool, other position indicators or signal inducing devices may be used replacing the housing and insert magnets. Examples of such devices include, but are not limited to, radio frequency identification (RFID) devices, radioactive pills, and ferromagnetic components. Relative positions of the signal inducing devices are detected by conveying a logging tool containing one or more sensors responsive to the signal inducing device.